Get more pixels (click on buttons) so you can spread (hover over) RED over the canvas!
You got 0 pixels!
pixel/click < Spread || pixel/tick < 0.5*pixel/click || Spread < 200
Density < 0.75*Spread || PixelSize < 0.1*pixel/click
Spread is the area around your mouse where pixels can land, Density is how much pixels you paint per tick
!warning: Make sure you have enough pixels/sec before upgrading pixelSize (it has some naughty effects)